Glass for manufacturing automotive and architectural glazings is generally produced by the well-known float glass process. The continuous float glass ribbon so produced is cut into glass sheets of various sizes which are thereafter conveyed to fabrication facilities where the glass sheets are subjected to further processing such as, for example, painting, coating, bending, tempering, annealing, etc.
Roller conveyors conveniently are used in the glass industry for conveying glass sheets from one processing location to another. It is well-known to employ a plurality of conveyors, in the form of a main-line conveyor and a series of spur-line conveyors which lie perpendicular to the main-line conveyor, for sorting the glass sheets and for removing a particular glass sheet from a main-line roller conveyor and selectively conveying it to a particular location via a spur-line roller conveyor. The difficulty in transferring a glass sheet from a first roller conveyor to a second roller conveyor lying perpendicular to the first roller conveyor results from the fact that the axes of the rollers of the first conveyor are perpendicular to the axes of the rollers of the second conveyor.
In the glass industry, it is well-known to transfer sheets of glass from one roller conveyor to another perpendicularly oriented roller conveyor using a perforated vacuum platen. Air is evacuated from the top-side of the platen utilizing conventional vacuum equipment and associated piping. The evacuated platen is superposed above the glass sheet which has come to rest on the first roller conveyor, lowered to contact the glass sheet, and the glass sheet thereby is lifted by engagement with the bottom surface of the platen. The platen, having the glass sheet adhered thereto, is lifted away from the first conveyor, translated in a direction generally parallel to the axes of the rollers of the first roller conveyor to a position above the rollers of the second roller conveyor, and lowered so as to deposit the glass sheet upon the rollers of the second conveyor. The vacuum is reduced and the platen is removed from engagement with the glass sheet.
Use of a perforated vacuum platen tends to mar the surface of the glass, and requires a large amount of energy to operate. Additionally, the complexity of such a system requires a great deal of maintenance, resulting in extended periods of time during which glass sheets cannot be transferred to those spur-line roller conveyors served by the broken-down vacuum platen system.
U.S. Pat. No. 4,205,755 to Timmons et al. discloses a device for transferring a glass sheet from one conveyor to a parallel conveyor, comprising a pivioting glass handling member which additionally turns the glass sheet over as it is being transferred from the first to the second conveyor. Such a device, however, would not be useful for transferring a glass sheet from one roller conveyor to a perpendicularly oriented roller conveyor.
U.S. Pat. No. 4,010,843 to Lucas discloses a device for transferring a load from the end of a first conveyor to a second perpendicularly oriented conveyor. The device comprises lifting elements which are disposed intermediate adjacent rollers of the second conveyor. These elements are lifted to project above the rollers of the second conveyor and lift the leading edge of the load at the end of the first conveyor. The lifting elements are then moved in a direction away from the first conveyor thereby dragging the load axially over the rollers of the second conveyor. When the load is transferred to the second conveyor, the lifting elements are lowered allowing the full weight of the load to rest upon the rollers of the second conveyor. Such an apparatus is only usable, however, for transferring a load to a second conveyor from the end of a first conveyor. It could not be used to transfer a load from any location along a main-line roller conveyor to a perpendicularly oriented spur-line roller conveyor. Furthermore, the process of dragging the load across the rollers of the second conveyor would mar the surface of certain types of conveyed articles such as, for example, glass sheets.
It would be desirable to devise a method and apparatus for transferring glass sheets from any location along a main-line roller conveyor to a spur-line roller conveyor lying perpendicular to the main-line conveyor, without the use of a perforated vacuum platen. Such a device conveniently would not abrade the surfaces of the glass sheets.